A fungus originally from East Asia has been discovered in leaf litter under ash trees across Europe, where it has been spreading quietly for several months. This fungus, known as chalara, thrives in the leaf litter at the base of ash trees and releases spores in the spring through the wind. The spores travel to the still-green leaves of ash trees, where they begin to infect the tree, progressing from the leaves to the branches. This causes necroses—areas of dead tissue—which weaken the tree's structure. Currently, there is no effective fungicide or phytosanitary measure that can stop the aerial spread of this pathogen on a large scale. Chalara naturally coexists with local ash tree species in East Asia without causing significant harm, but European ash trees have no prior exposure to the fungus and are highly susceptible. In the spring, the fungus forms white fructifications called apothecia on the leaf stalks of fallen leaves, releasing ascospores. These spores are carried by the wind from May to June, settling on the still-green leaves of ash trees. By the end of summer, the fungus spreads from the leaves to the shoots and branches, causing necrotic damage. The infected branches turn a distinctive brown-orange color, a visible sign of the infection. During winter, the fungus does not die but instead forms a black, protective structure called a pseudosclerotium, which remains dormant in the leaf litter until the next spring. The spread of chalara is primarily through wind-borne spores, which are difficult to contain with physical barriers. The spores are produced in large quantities and can travel up to 1 to 2 kilometers, with some reaching even further under favorable wind conditions. Efforts to cut down infected trees are largely ineffective, as the spores can still spread via wind. The Ministry of Agriculture has confirmed that new plantings of ash trees should be avoided, as they are likely to become sources of contamination. Pruning and other phytosanitary measures are also ineffective due to the widespread presence of ash trees and the efficiency of the pathogen’s spread. Despite the challenges, the fate of ash trees varies depending on their environment. In urban areas, the impact of chalara is less severe, as regular leaf removal on artificial soils prevents the disease cycle from completing. In contrast, dense ash forests provide ideal conditions for the fungus to spread from one tree to another. However, even in these environments, the mortality rate is generally low, with many trees surviving but suffering damage. Researchers are exploring the possibility that some ash trees may have natural resistance to chalara. While the reasons for this resistance are not yet fully understood, the presence of resistant individuals offers hope for the long-term survival of the species. For now, the best strategy remains observation and allowing natural selection to take its course, as no effective treatment is currently available.